Imaging transducer assembly

ABSTRACT

The present invention is generally directed towards an imaging transducer assembly. Generally, the imaging transducer assembly is combined with a sensor of a medical positioning system. In one aspect, the transducer assembly and the sensor share the same voltage source. In another aspect of the invention, the sensor surrounds a portion of the imaging transducer assembly, forming a housing that reinforces the assembly.

FIELD OF THE INVENTION

The field of the invention relates to medical imaging systems, and moreparticularly to an improved imaging transducer assembly.

BACKGROUND OF THE INVENTION

Intraluminal, intracavity, intravascular, and intracardiac treatmentsand diagnosis of medical conditions utilizing minimally invasiveprocedures are effective tools in many areas of medical practice. Theseprocedures are typically performed using imaging and treatment cathetersthat are inserted percutaneously into the body and into an accessiblevessel of the vascular system at a site remote from the vessel or organto be diagnosed and/or treated, such as the femoral artery. The catheteris then advanced through the vessels of the vascular system to theregion of the body to be treated. The catheter may be equipped with animaging device, typically an ultrasound imaging device, which is used tolocate and diagnose a diseased portion of the body, such as a stenosedregion of an artery. For example, U.S. Pat. No. 5,368,035, issued toHamm et al., the disclosure of which is incorporated herein byreference, describes a catheter having an intravascular ultrasoundimaging transducer.

FIG. 1 a shows an example of an imaging transducer assembly 1 known inthe art. The imaging transducer 1 is typically within the lumen 60 of aguidewire (partially shown), having an outer tubular wall member 5. Theimaging transducer assembly 1 includes a coaxial cable 110, having acenter conductor wire 120 and an outer shield wire 140, shown in FIG. 1b. A conductive wire, having a diameter of approximately 500 microns, iswrapped around the coaxial cable 110, forming a coil, which functions asa drive shaft 10. Connected to the distal end of the drive shaft 10 is astainless steel housing 20, which serves to reinforce the structure ofthe imaging transducer assembly 1. Surrounding the coaxial cable 110,within the housing 20 is a silver epoxy 30, a conductive material. Thus,the housing 20 is electrically coupled to the shield wire 140 of thecoaxial cable 110 via the epoxy 30. On the distal end of the silverepoxy 140 is an insulating substance, a non-conductive epoxy 35.

On the distal end of the non-conductive epoxy 35 is a layer ofpiezoelectric crystal (“PZT”) 80, “sandwiched” between a conductiveacoustic lens 70 and a conductive backing material 90, formed from anacoustically absorbent material (e.g., an epoxy substrate havingtungsten particles). The acoustic lens 70 is electrically coupled withthe center conductor wire 120 of the coaxial cable 110 via a connector40 that is insulated from the silver epoxy 30 and the backing material90 by the non-conductive epoxy 35. The backing material 90 is connectedto the steel housing 20. It is desirable for the imaging transducerassembly 1 to be surrounded by a sonolucent media. Thus, the lumen 60 ofthe guidewire is also filled with saline around the assembly 1. Thedriveshaft 10, the housing 20, and the acoustic lens 70 are exposed tothe saline. During operation, the PZT layer 80 is electrically excitedby both the backing material 90 and the acoustic lens 70. The backingmaterial 90 receives its charge from the shield wire 140 of the coaxialcable 110 via the silver epoxy 30 and the steel housing 30, and theacoustic lens 70, which may also be silver epoxy, receives its chargefrom the center conductor wire 120 of the coaxial cable 110 via theconnector 40, which may be silver epoxy as well.

Turning to FIG. 1 c, the imaging transducer assembly 1 can be depictedas a simple electric circuit having a voltage source 150, two terminals,A and B, a load 81 caused by the saline filled in the lumen 60, and thePZT load 80. The saline load 81 and the PZT load 80 are charged by thevoltage source 150 via the two terminals, A and B, representing theshield wire 140 and the center conductor wire 120 of the coaxial cable110, respectively. In addition, transducer control circuitry (notshown), which may include a signal processor to handle imaging signals,may also be coupled with the transducer assembly 1.

The imaging transducer is an effective tool for obtaining thecross-sectional image of a blood vessel. However, in some instances, itmay be desirable to obtain more information, such as a three-dimensionallongitudinal profile of the same blood vessel in addition to thecross-sectional image. Accordingly, an improved imaging transducerassembly would be desirable.

SUMMARY OF THE INVENTION

The improved imaging device is intended for use within the lumen of ablood vessel. Generally, the imaging transducer assembly is combinedwith a sensor of a medical positioning system.

In one embodiment, the imaging transducer assembly and the sensor may beelectrically charged using a first and second terminal. The imagingtransducer assembly may be coupled with a coaxial cable having a centerwire and an outer wire, wherein one of the first and second terminals iscoupled with the center wire and the other of the first and secondterminal is coupled with the outer wire. Further, at least one of thefirst and second terminals is insulated from any sonolucent media incontact with the imaging transducer assembly. Further, the sensorsurrounds the imaging transducer assembly, forming a housing structureto reinforce the assembly.

In another embodiment, a method includes obtaining the cross-sectionalimage of a blood vessel and at substantially the same time, obtainingthe longitudinal profile of the same blood vessel.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better appreciate how the above-recited and other advantagesand objects of the present inventions are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof, which are illustrated in theaccompanying drawings. It should be noted that the components in thefigures are not necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like reference numerals designate corresponding parts throughout thedifferent views. However, like parts do not always have like referencenumerals. Moreover, all illustrations are intended to convey concepts,where relative sizes, shapes and other detailed attributes may beillustrated schematically rather than literally or precisely.

FIG. 1 a is a cross-sectional side view of an imaging transducerassembly known in the art.

FIG. 1 b is a cross-sectional view of the coaxial cable within the priorart imaging transducer assembly of FIG. 1 a.

FIG. 1 c is a simplified diagram of an electrical circuit formed by theprior art imaging transducer assembly of FIG. 1 a.

FIG. 2 a is an illustration of a prior art medical positioning system.

FIG. 2 b is a simplified diagram of an electrical circuit formed by asensor of a prior art medical positioning system.

FIG. 3 a is cross-sectional side view of an imaging transducer assemblyin accordance with an exemplary embodiment of the present invention.

FIG. 3 b is a cross-sectional view of a coaxial cable within the imagingtransducer assembly of FIG. 3 a.

FIG. 3 c is a simplified diagram of an electrical circuit formed by theimaging transducer assembly of FIG. 3 a.

FIG. 4 is a partial cross-sectional side view of a catheter inaccordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Described below is an improved imaging transducer assembly.

In some instances, it may be desirable to be able to obtain not only thecross-sectional image of a blood vessel, but also information such asthe three-dimensional longitudinal profile of the same blood vessel. Oneapproach in obtaining such additional information is to use a medicalpositioning system, which is generally known in the art. Turning to FIG.2 a, a prior art medical positioning system 240 is illustrated. Thesystem 240 generally includes a plurality of transmitter and/or receivernodes 250 that may be arranged around a patient. For instance, the nodes250 may be arranged on a framework of towers that surround a patient.The system 240 further includes one or more sensors 260, which areconfigured to send and/or receive electro-magnetic, orelectro-mechanical, signals to and/or from the transmitter/receivernodes 250.

A sensor 260, coupled with a guidewire (partially shown), may be placedwithin the blood vessel of a patient's body. The signals exchangedbetween the sensor 260 and the nodes 250 function as navigationalsignals which, as can be appreciated by one of ordinary skill in theart, may be used to determine the position of the sensor 260 within thepatient's body. In other words, the sensor 260 transmits navigationalsignals to the nodes 250, and a processor (not shown) coupled with thenodes 250 determines the position of the sensor 260 based on the signalsreceived by the nodes 250. Alternatively, or in addition, the nodes 250may send navigational signals to the sensor 260, and a processor (notshown) coupled with the sensor 260 determines the position of the sensor260 within the patient's body based on the signals sent by the nodes250. The medical positioning system 240 can track and record theposition of the sensor 260 as it is moved throughout a patient's bloodvessel, thus providing a longitudinal profile of the blood vessel.

Turning to FIG. 2 b, the sensor 260 is depicted as a simplifiedelectrical circuit having two terminals, A and B, an “antenna” load, anda load 270. The antenna is the portion of the sensor 260 where asubstantial amount of the navigational signals are sent and/or received.If the sensor 260 is configured to send electromagnetic signals to thenodes 250, then to facilitate the electromagnetic broadcast, the load270 may be a voltage source 270, which charges the antenna via theterminals A and B. Alternatively, if the sensor 260 is configured toreceive electromagnetic signals from the nodes 250, then the load 270may be sensor circuitry, which may include a signal processor (notshown) to handle navigational signals.

In one example preferred embodiment of the improved imaging transducerassembly shown in FIGS. 3 a and 3 b, a sensor of a medical positioningsystem may be combined with an imaging transducer to form atransducer/sensor assembly 300. Turning to FIG. 3 a, a cross-sectionalside view of a transducer/sensor assembly 300 is shown in a lumen 305 ofthe distal portion of a guidewire or catheter assembly (partially shown)having an outer tubular wall 301. The transducer/sensor assembly 300includes a coaxial cable 410, having a center conductor wire 420, and anouter shield wire 430, as shown in FIG. 3 b. The center conductor wire420 is insulated from the outer shield wire 430. In addition, the shieldwire 430 is surrounded by an insulating jacket 440. It should be notedthat numerous alternative cable configurations may be used; for example,a cable having “twisted pair” wires may be used instead of a coaxialcable.

Turning back to FIG. 3 a, surrounding the coaxial cable 410 is a layerof insulating material, such as a non-conductive epoxy 330. Surroundingthe epoxy 330 is a drive shaft 310, which is a conductive wire woundaround the epoxy 330/coaxial cable 350 to form a first coil shape 310.Preferably, the conductive wire is stainless and has a diameter ofapproximately 500 microns. Thus, the coaxial cable 350 is conductivelyinsulated from the drive shaft 310.

The distal end of the transducer/sensor assembly 300 includes anelectrically conductive backing material 390, having a top, bottom andcenter, which may be formed from an acoustically absorbent material (forexample, an epoxy substrate having tungsten particles). The center ofthe backing material 390 surrounds a shield pellet 400, which iselectrically coupled to the shield wire 430 at the distal end of thecoaxial cable 410. The top of the backing material 390 is coupled to thebottom of a layer of piezoelectric crystal (PZT) 380. The top of the PZTlayer 380 is coupled to a conductive acoustic lens 370, which mayinclude silver epoxy. The acoustic lens 370 is electrically coupled tothe center conductor wire 420 of the coaxial cable 410 via a connector360, which may include silver epoxy, surrounding the non-conductiveepoxy 330 such that the connector 360 is insulated from the backingmaterial 390.

The transducer/sensor assembly 300 further includes a sensor 320 of amedical positioning system. The “antenna” portion of the sensor 320 isan insulated conductive wire 325. The wire 325 may also have magneticqualities. The wire 325 is tightly wrapped around a portion of thedistal end of the coaxial cable 410 and non-conductive epoxy 330, and isalso tightly wrapped around the distal end of the drive shaft 310,forming a second coil shape. The second coil shape desirably provides aninductance for the antenna portion of the sensor 320 when charged toincrease its ability to send and receive electro-magnetic signals. Thesecond coil shape also serves as a housing to reinforce thetransducer/sensor assembly 300. However, it should be noted that theantenna portion of the sensor 320 may have a variety of other shapes andconfigurations. For example, the antenna portion of the sensor 320 maybe a solid structure. The wire 325 is preferably copper andapproximately 10 microns in diameter. The small diameter of the wire 325allows the sensor 320 to have a small impact on the dimensions of thetransducer/sensor assembly 300, thus allowing the transducer/sensorassembly 300 to still work within the lumen 305 of the guidewire orcatheter assembly.

The two ends of the wire 325 are terminals that receive an electriccharge. One end 350 of the wire 325 is coupled to the connector 360 thatelectrically couples the acoustic lens 370 with the center conductorwire 420 of the coaxial cable 410. The other end 340 of the wire 325 iscoupled to the shield wire 430 of the coaxial cable 410, surrounded andinsulated from the drive shaft 310 and the connector 360 by thenon-conductive epoxy 330.

To facilitate the operation of the imaging transducer portion of thetransducer/sensor assembly 300, the lumen 305 of the guidewire orcatheter assembly is preferably filled with a sonolucent media, such assaline. It is desirable to have at least one of the ends 350, 340 of thewire 325 of the sensor 320 be insulated from the saline within the lumen305 because if both ends, 350 and 340, were exposed to the saline, thesemi-conductive nature of the saline might shunt the ends, 350 and 340,thus undesirably “shorting out” the antenna of the sensor 320, and/oraffecting the signal-to-noise ratio of the navigational signals. Inlight of this, the transducer/sensor assembly 300 preferably has one end340 of the wire 325 of the sensor insulated from the drive shaft 310,backing material 390, connector 360, and saline by the non-conductiveepoxy 330. Further, the coil portion of the wire 325 is also insulatedfrom the driveshaft 310 and the saline in the lumen 305 by anon-conductive material. The other end 350 of the wire 325, however, maybe exposed to the saline.

During the operation of the transducer/sensor assembly 300, the PZTcrystal 380 is electrically excited by both the backing material 390,charged through the shield wire 430, and the acoustic lens 370, chargedthrough the center conductor wire 420. In addition, the antenna portion325 of the sensor 320 is also charged by the shield wire 430 and thecenter conductor wire 420. If the sensor 320 is configured to sendelectromagnetic signals to nodes of a medical positioning system (notshown), then the charge may facilitate a broadcast. However, if thesensor 320 is configured to receive electromagnetic signals from one ormore nodes of a medical positioning system (not shown), then separatecircuitry including a signal processor may be used to filter and extractthe desired electromagnetic signals. Thus, turning to FIG. 3 c, theassembly 300 is depicted as a simplified electric circuit having avoltage source 530, the load of the PZT layer 380, the load of theantenna portion 325 of the sensor 320, which is in parallel with theload of the PZT layer 380, sensor circuitry 531, which may include asignal processor (not shown) to receive and process electromagneticsignals, i.e., navigational signals, from the sensor 320, as would beknown to a person of skill in the art, transducer circuitry 532, whichmay also include a signal processor (not shown) to process imagingsignals from the imaging transducer, and terminals A and B. Terminals Aand B represent the center conductor wire 420 and the shield wire 430 ofthe coaxial cable 410, respectively. Other features and circuits mayalso be added as desired.

Turning to FIG. 4, the transducer/sensor assembly 300 may be placed in adistal portion 520 of a guidewire 500. The guidewire 500 may comprise aguidewire body 302 in the form of a flexible, elongate tubular member,having an outer wall 301. The guidewire body 302 may be formed of anymaterial known in the art including nitinol hypotube, metal alloys,composite materials, plastics, braided polyimide, polyethylene, peekbraids, stainless steel, or other superelastic materials.

The length of the guidewire 500 may vary depending on the application.In a preferred embodiment, the length of the guidewire 500 is between 30cm and 300 cm. A catheter (not shown) may be configured to use severaldifferent diameters of guidewires 500. For example, the guidewire 500may have a diameter of 0.010, 0.014, 0.018, or 0.035 inches. Typically,the diameter of the guidewire 500 is uniform.

A proximal portion 510 of the guidewire 500 may be adapted to connect tocircuitry (not shown) that processes imaging signals from the imagingtransducer and/or circuitry (not shown) that processes navigationalsignals from the sensor 320, such circuits being well known.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Forexample, the reader is to understand that the specific ordering andcombination of process actions described herein is merely illustrative,and the invention can be performed using different or additional processactions, or a different combination or ordering of process actions. Forexample, this invention is particularly suited for applicationsinvolving medical imaging devices, but can be used on any designinvolving imaging devices in general. As a further example, each featureof one embodiment can be mixed and matched with other features shown inother embodiments. Additionally and obviously, features may be added orsubtracted as desired. Accordingly, the invention is not to berestricted except in light of the attached claims and their equivalents.

1. An imaging catheter having distal and proximal ends and a lumen, comprising: an imaging transducer assembly located within the lumen of a distal portion of the catheter, the imaging transducer assembly including an imaging transducer; and a sensor coupled to the imaging transducer within the lumen, the sensor adapted to communicate with a medical positioning system, wherein the sensor includes an antenna portion having first and second terminals, and wherein the imaging transducer assembly has a first and second transducer terminal, the first transducer terminal being coupled to a first wire and the second transducer terminal being coupled to a second wire, the imaging transducer assembly and the sensor are coupled to the first and second terminals, the first wire is coupled with one of the first and second terminals and the second wire is coupled with the other of the first and second terminals.
 2. The imaging catheter of claim 1, wherein the first wire is a center wire of a coaxial cable and the second wire is an outer wire of the coaxial cable.
 3. The imaging catheter of claim 1, wherein the first wire is one wire of a cable with twisted pair wires and the second wire is the other wire of the cable with twisted pair wires.
 4. An imaging device for use within the lumen of a blood vessel comprising: a coaxial cable having an inner wire and an outer wire; a non-conductive epoxy layer surrounding the coaxial cable; a drive shaft coil, having distal and proximal ends, surrounding the non-conductive epoxy layer; an imaging transducer assembly coupled to the distal portion of the coaxial cable, wherein the imaging transducer includes a first and second terminal; and a sensor having an antenna portion coupled to the first and second terminals; wherein one of the first and second terminals is coupled with the inner wire of the coaxial cable and the other of the first and second terminals is coupled with the outer wire.
 5. The imaging device of claim 4, wherein the sensor is a conductive wire wrapped around the drive shaft coil, forming a coil shape.
 6. The imaging device of claim 4, wherein the antenna portion of the sensor surrounds the drive shaft forming a housing around the imaging transducer assembly.
 7. The imaging device of claim 4, wherein the antenna portion of the sensor is a conductive wire.
 8. The imaging device of claim 7, wherein the wire is copper.
 9. The imaging device of claim 4, wherein the imaging transducer assembly comprises an acoustic lens coupled with a piezoelectric crystal layer, and the piezoelectric crystal layer is coupled with a backing material.
 10. The imaging device of claim 9, wherein the backing material comprises tungsten.
 11. The imaging device of claim 9, wherein acoustic lens is electrically coupled with one of the first and second terminals and the backing material is electrically coupled with the other of the first and second terminals.
 12. The imaging device of claim 4, further comprising a sonolucent media in the lumen, wherein at least one of the first and second terminals is insulated from the sonolucent media in contact with the imaging transducer assembly.
 13. A medical imaging system comprising: a medical positioning system; and an imaging device adapted to be inserted into a lumen of a body, the imaging device including: a catheter having distal and proximal ends and a lumen; an imaging transducer assembly located within the lumen of a distal portion of the catheter, the imaging transducer assembly including an imaging transducer; and a sensor coupled to the imaging transducer within the lumen of the catheter, the sensor adapted to communicate with the medical positioning system, wherein the sensor includes an antenna portion having first and second terminals, and wherein the imaging transducer assembly has a first and second transducer terminal, the first transducer terminal being coupled to a first wire and the second transducer terminal being coupled to a second wire, the imaging transducer assembly and the sensor are coupled to the first and second terminals, the first wire is coupled with one of the first and second terminals and the second wire is coupled with the other of the first and second terminals.
 14. The medical imaging system of claim 13, wherein the first wire is a center wire of a coaxial cable and the second wire is an outer wire of the coaxial cable.
 15. The medical imaging system of claim 14, wherein the first wire is one wire of a cable with twisted pair wires and the second wire is the other wire of the cable with twisted pair wires. 